jlme

CRAN status Lifecycle: experimental R-CMD-check test-coverage codecov

Julia (mixed-effects) regression modelling from R. Powered by the {JuliaConnectoR} R package and Julia libraries GLM, StatsModels, and MixedModels.

Installation

You can install the development version of {jlme} from GitHub with:

# install.packages("remotes")
remotes::install_github("yjunechoe/jlme")

{jlme} is experimental and under active development: see NEWS.md for the latest updates.

Setup

library(jlme)
jlme_setup()

Using {jlme} requires a prior installation of the Julia programming language, which can be downloaded from either the official website or using the command line utility juliaup.

If you are encountering issues with setting up Julia, please make sure that you’re have the latest version (>=1.1.4) of the {JuliaConnectoR} package installed and see ?JuliaConnectoR::`Julia-Setup` for troubleshooting.

Usage (table of contents)

Fit models

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Once set up, (g)lm() and (g)lmer complements in Julia are available via jlm() and jlmer(), respectively.

Fixed effects models

jlm() with lm()/glm() syntax:

# lm(mpg ~ hp, mtcars)
jlm(mpg ~ hp, mtcars)
#> <Julia object of type StatsModels.TableRegressionModel>
#> 
#> mpg ~ 1 + hp
#> 
#> ────────────────────────────────────────────────────────────────────────────
#>                   Coef.  Std. Error      z  Pr(>|z|)   Lower 95%   Upper 95%
#> ────────────────────────────────────────────────────────────────────────────
#> (Intercept)  30.0989      1.63392    18.42    <1e-75  26.8964     33.3013
#> hp           -0.0682283   0.0101193  -6.74    <1e-10  -0.0880617  -0.0483948
#> ────────────────────────────────────────────────────────────────────────────

Contrasts in factor columns are preserved:

x <- mtcars

# Sum code `am`
x$am_sum <- factor(x$am)
contrasts(x$am_sum) <- contr.sum(2)
# Helmert code `cyl`
x$cyl_helm <- factor(x$cyl)
contrasts(x$cyl_helm) <- contr.helmert(3)
colnames(contrasts(x$cyl_helm)) <- c("4vs6", "4&6vs8")

jlm(mpg ~ am_sum + cyl_helm, x)
#> <Julia object of type StatsModels.TableRegressionModel>
#> 
#> mpg ~ 1 + am_sum + cyl_helm
#> 
#> ───────────────────────────────────────────────────────────────────────────────
#>                      Coef.  Std. Error      z  Pr(>|z|)  Lower 95%    Upper 95%
#> ───────────────────────────────────────────────────────────────────────────────
#> (Intercept)       20.6739     0.572633  36.10    <1e-99   19.5516   21.7963
#> am_sum: 1         -1.27998    0.648789  -1.97    0.0485   -2.55158  -0.00837293
#> cyl_helm: 4vs6    -3.07806    0.767861  -4.01    <1e-04   -4.58304  -1.57308
#> cyl_helm: 4&6vs8  -2.32983    0.414392  -5.62    <1e-07   -3.14203  -1.51764
#> ───────────────────────────────────────────────────────────────────────────────

Mixed effects models

jlmer() with lmer()/glmer() syntax:

# lme4::lmer(Reaction ~ Days + (Days | Subject), lme4::sleepstudy)
jlmer(Reaction ~ Days + (Days | Subject), lme4::sleepstudy, REML = TRUE)
#> <Julia object of type LinearMixedModel>
#> 
#> Linear mixed model fit by REML
#>  Reaction ~ 1 + Days + (1 + Days | Subject)
#>  REML criterion at convergence: 1743.6282719599653
#> 
#> Variance components:
#>             Column    Variance Std.Dev.   Corr.
#> Subject  (Intercept)  612.10016 24.74066
#>          Days          35.07171  5.92214 +0.07
#> Residual              654.94001 25.59180
#>  Number of obs: 180; levels of grouping factors: 18
#> 
#>   Fixed-effects parameters:
#> ──────────────────────────────────────────────────
#>                 Coef.  Std. Error      z  Pr(>|z|)
#> ──────────────────────────────────────────────────
#> (Intercept)  251.405      6.8246   36.84    <1e-99
#> Days          10.4673     1.54579   6.77    <1e-10
#> ──────────────────────────────────────────────────
# lme4::glmer(r2 ~ Anger + Gender + (1 | id), lme4::VerbAgg, family = "binomial")
jlmer(r2 ~ Anger + Gender + (1 | id), lme4::VerbAgg, family = "binomial")
#> <Julia object of type GeneralizedLinearMixedModel>
#> 
#> Generalized Linear Mixed Model fit by maximum likelihood (nAGQ = 1)
#>   r2 ~ 1 + Anger + Gender + (1 | id)
#>   Distribution: Bernoulli{Float64}
#>   Link: LogitLink()
#> 
#>    logLik    deviance     AIC       AICc        BIC    
#>  -4748.2525  9496.5050  9504.5050  9504.5102  9532.2401
#> 
#> Variance components:
#>       Column   VarianceStd.Dev.
#> id (Intercept)  1.12074 1.05865
#> 
#>  Number of obs: 7584; levels of grouping factors: 316
#> 
#> Fixed-effects parameters:
#> ────────────────────────────────────────────────────
#>                   Coef.  Std. Error      z  Pr(>|z|)
#> ────────────────────────────────────────────────────
#> (Intercept)  -1.10115     0.280681   -3.92    <1e-04
#> Anger         0.0462741   0.0134906   3.43    0.0006
#> Gender: M     0.260057    0.153847    1.69    0.0910
#> ────────────────────────────────────────────────────

Diagnose models

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Supports {broom}-style tidy() and glance() methods for Julia regression models.

Summarize model fit

Get information about model components with tidy()

# Note that MixedModels/`jlmer()` defaults to ML (REML=false)
jmod <- jlmer(Reaction ~ Days + (Days | Subject), lme4::sleepstudy)
tidy(jmod)
#>      effect    group                  term     estimate std.error statistic
#> 1     fixed     <NA>           (Intercept) 251.40510485  6.632258 37.906414
#> 2     fixed     <NA>                  Days  10.46728596  1.502236  6.967806
#> 12 ran_pars  Subject       sd__(Intercept)  23.78046792        NA        NA
#> 3  ran_pars  Subject cor__(Intercept).Days   0.08133207        NA        NA
#> 21 ran_pars  Subject              sd__Days   5.71682816        NA        NA
#> 11 ran_pars Residual       sd__Observation  25.59182388        NA        NA
#>          p.value
#> 1  2.017794e-314
#> 2   3.219214e-12
#> 12            NA
#> 3             NA
#> 21            NA
#> 11            NA

Get goodness-of-fit measures of a model with glance()

glance(jmod)
#>   nobs df    sigma    logLik      AIC      BIC deviance df.residual
#> 1  180  6 25.59182 -875.9697 1763.939 1783.097 1751.939         174

Inspect model objects

Check singular fit

issingular(jmod)
#> [1] FALSE

List all properties of a MixedModel object (properties are accessible via $)

propertynames(jmod)
#>  [1] "A"         "b"         "beta"      "betas"     "corr"      "dims"     
#>  [7] "feterm"    "formula"   "L"         "lambda"    "lowerbd"   "objective"
#> [13] "optsum"    "parmap"    "PCA"       "pvalues"   "rePCA"     "reterms"  
#> [19] "sigma"     "sigmarhos" "sigmas"    "sqrtwts"   "stderror"  "theta"    
#> [25] "u"         "vcov"      "X"         "Xymat"     "y"         "β"        
#> [31] "βs"        "θ"         "λ"         "σ"         "σs"        "σρs"

Check optimization summary

jmod$optsum
#> <Julia object of type OptSummary{Float64}>
#> Initial parameter vector: [1.0, 0.0, 1.0]
#> Initial objective value:  1784.642296192471
#> 
#> Optimizer (from NLopt):   LN_BOBYQA
#> Lower bounds:             [0.0, -Inf, 0.0]
#> ftol_rel:                 1.0e-12
#> ftol_abs:                 1.0e-8
#> xtol_rel:                 0.0
#> xtol_abs:                 [1.0e-10, 1.0e-10, 1.0e-10]
#> initial_step:             [0.75, 1.0, 0.75]
#> maxfeval:                 -1
#> maxtime:                  -1.0
#> 
#> Function evaluations:     57
#> Final parameter vector:   [0.9292213025841999, 0.018168360086059557, 0.22264488361408383]
#> Final objective value:    1751.9393444646894
#> Return code:              FTOL_REACHED

Assess uncertainty

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Functions parametricbootstrap() and profilelikelihood() can be used to assess the variability of parameter estimates.

Parametric bootstrap

Experimental support for MixedModels.parametricbootstrap via parametricbootstrap():

samp <- parametricbootstrap(jmod, nsim = 100L, seed = 42L)
samp
#> <Julia object of type MixedModelBootstrap{Float64}>
#> MixedModelBootstrap with 100 samples
#>      parameter  min        q25         median     mean       q75        max
#>    ┌────────────────────────────────────────────────────────────────────────────
#>  1 │ β1         228.0      246.58      250.863    250.977    256.082    264.406
#>  2 │ β2         6.72055    9.91274     10.8382    10.696     11.6725    13.7769
#>  3 │ σ          21.6856    24.6536     25.6211    25.838     26.7439    30.5968
#>  4 │ σ1         3.57556    17.8908     22.1421    21.5799    25.6259    31.9446
#>  5 │ σ2         1.63637    4.53406     5.36349    5.47536    6.38651    8.34052
#>  6 │ ρ1         -0.739267  -0.226513   0.120712   0.107686   0.389495   1.0
#>  7 │ θ1         0.146373   0.675859    0.845334   0.839596   1.02343    1.29287
#>  8 │ θ2         -0.18147   -0.0508505  0.0248657  0.0155747  0.0708033  0.226194
#>  9 │ θ3         0.0        0.156785    0.193042   0.188678   0.238505   0.334108
tidy(samp)
#>     effect    group                  term     estimate    conf.low  conf.high
#> 1    fixed     <NA>           (Intercept) 251.40510485 240.8972974 263.280668
#> 2    fixed     <NA>                  Days  10.46728596   7.7302901  13.540729
#> 5 ran_pars  Subject       sd__(Intercept)  23.78046792  12.5974975  31.944579
#> 4 ran_pars  Subject cor__(Intercept).Days   0.08133207  -0.5948863   1.000000
#> 6 ran_pars  Subject              sd__Days   5.71682816   3.6653412   8.073549
#> 3 ran_pars Residual       sd__Observation  25.59182388  22.4968576  29.124647

Profiling

Experimental support for MixedModels.profile via profilelikelihood():

prof <- profilelikelihood(jmod)
prof
#> <Julia object of type MixedModelProfile{Float64}>
#> MixedModelProfile -- Table with 11 columns and 176 rows:
#>       p  ζ          β1       β2       σ        σ1       σ2       ρ1           ⋯
#>     ┌──────────────────────────────────────────────────────────────────────────
#>  1  │ σ  -4.365     251.405  10.4673  20.1933  25.5128  5.97319  -0.0159232   ⋯
#>  2  │ σ  -3.77902   251.405  10.4673  20.8002  25.3434  5.94786  -0.00711109  ⋯
#>  3  │ σ  -3.20526   251.405  10.4673  21.4255  25.1627  5.92133  0.00263598   ⋯
#>  4  │ σ  -2.64336   251.405  10.4673  22.0695  24.9702  5.89214  0.0129078    ⋯
#>  5  │ σ  -2.09298   251.405  10.4673  22.7328  24.7636  5.86167  0.0241968    ⋯
#>  6  │ σ  -1.55378   251.405  10.4673  23.4162  24.5426  5.82871  0.0366992    ⋯
#>  7  │ σ  -1.02542   251.405  10.4673  24.12    24.3063  5.79389  0.0501628    ⋯
#>  8  │ σ  -0.507597  251.405  10.4673  24.845   24.0525  5.75669  0.0649969    ⋯
#>  9  │ σ  0.0        251.405  10.4673  25.5918  23.7805  5.71683  0.0813321    ⋯
#>  10 │ σ  0.497684   251.405  10.4673  26.3611  23.4885  5.6743   0.0993046    ⋯
#>  11 │ σ  0.985728   251.405  10.4673  27.1534  23.1743  5.62882  0.119204     ⋯
#>  12 │ σ  1.46442    251.405  10.4673  27.9696  22.836   5.5802   0.141262     ⋯
#>  13 │ σ  1.93402    251.405  10.4673  28.8104  22.4727  5.52809  0.165869     ⋯
#>  14 │ σ  2.39481    251.405  10.4673  29.6763  22.0799  5.47226  0.193415     ⋯
#>  15 │ σ  2.84704    251.405  10.4673  30.5684  21.6557  5.41243  0.224387     ⋯
#>  16 │ σ  3.29094    251.405  10.4673  31.4872  21.196   5.34818  0.259442     ⋯
#>  17 │ σ  3.72677    251.405  10.4673  32.4337  20.6956  5.27882  0.299408     ⋯
#>  ⋮  │ ⋮      ⋮         ⋮        ⋮        ⋮        ⋮        ⋮          ⋮       ⋱
tidy(prof)
#>      effect    group            term   estimate   conf.low  conf.high
#> 1     fixed     <NA>     (Intercept) 251.405105 237.680694 265.129516
#> 2     fixed     <NA>            Days  10.467286   7.358653  13.575919
#> 12 ran_pars  Subject sd__(Intercept)  23.780468  14.381431  37.718099
#> 21 ran_pars  Subject        sd__Days   5.716828   0.000000   8.753389
#> 11 ran_pars Residual sd__Observation  25.591824  22.898262  28.858001

Julia interoperability

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Functions jl_get() and jl_put() transfers data between R and Julia.

Bring Julia objects into R

Example 1: extract PCA of random effects and return as an R list:

jmod$rePCA
#> <Julia object of type @NamedTuple{Subject::Vector{Float64}}>
#> (Subject = [0.5406660352881864, 1.0],)
jl_get(jmod$rePCA)
#> $Subject
#> [1] 0.540666 1.000000

Example 2: extract fitlog and plot

fitlog <- jl_get(jl("refit!(deepcopy(x); thin=1)", x = jmod)$optsum$fitlog)
thetas <- t(sapply(fitlog, `[[`, 1))
matplot(thetas, type = "o", xlab = "iterations")

Julia session

See information about the running Julia environment (e.g., the list of loaded Julia libraries) with jlme_status():

jlme_status()
#> jlme 0.4.0 
#> R version 4.4.1 (2024-06-14 ucrt) 
#> Julia Version 1.10.5
#> Commit 6f3fdf7b36 (2024-08-27 14:19 UTC)
#> Build Info:
#>   Official https://julialang.org/ release
#> Platform Info:
#>   OS: Windows (x86_64-w64-mingw32)
#>   CPU: 8 × 11th Gen Intel(R) Core(TM) i7-1165G7 @ 2.80GHz
#>   WORD_SIZE: 64
#>   LIBM: libopenlibm
#>   LLVM: libLLVM-15.0.7 (ORCJIT, tigerlake)
#> Threads: 1 default, 0 interactive, 1 GC (on 8 virtual cores)
#> Status `C:\Users\jchoe\AppData\Local\Temp\jl_QJShm4\Project.toml`
#>   [38e38edf] GLM v1.9.0
#>   [ff71e718] MixedModels v4.26.1
#>   [3eaba693] StatsModels v0.7.4
#>   [9a3f8284] Random

On setup, {jlme} loads GLM, StatsModels, and MixedModels, as well as those specified in jlme_setup(add). Other libraries such as Random (required for parametricbootstrap()) are loaded on an as-needed basis.

More with {JuliaConnectoR}

While users will typically not need to interact with {JuliaConnectoR} directly, it may be useful for extending {jlme} features with other packages in the Julia modelling ecosystem. A simple way to do that is to use juliaImport(), which creates makeshift bindings to any Julia library.

Here’s an example replicating a workflow using Effects.empairs for post-hoc pairwise comparisons:

# New model: 2 (M/F) by 3 (curse/scold/shout) factorial
jmod2 <- jlmer(
  r2 ~ Gender * btype + (1 | id),
  data = lme4::VerbAgg,
  family = "binomial"
)
jmod2
#> <Julia object of type GeneralizedLinearMixedModel>
#> 
#> Generalized Linear Mixed Model fit by maximum likelihood (nAGQ = 1)
#>   r2 ~ 1 + Gender + btype + Gender & btype + (1 | id)
#>   Distribution: Bernoulli{Float64}
#>   Link: LogitLink()
#> 
#>    logLik    deviance     AIC       AICc        BIC    
#>  -4341.4933  8682.9867  8696.9867  8697.0014  8745.5232
#> 
#> Variance components:
#>       Column   VarianceStd.Dev.
#> id (Intercept)  1.52160 1.23353
#> 
#>  Number of obs: 7584; levels of grouping factors: 316
#> 
#> Fixed-effects parameters:
#> ─────────────────────────────────────────────────────────────────
#>                               Coef.  Std. Error       z  Pr(>|z|)
#> ─────────────────────────────────────────────────────────────────
#> (Intercept)                0.738396   0.0956957    7.72    <1e-13
#> Gender: M                  0.404282   0.201612     2.01    0.0449
#> btype: scold              -1.01214    0.0742669  -13.63    <1e-41
#> btype: shout              -1.77376    0.0782721  -22.66    <1e-99
#> Gender: M & btype: scold   0.130832   0.156315     0.84    0.4026
#> Gender: M & btype: shout  -0.533658   0.168832    -3.16    0.0016
#> ─────────────────────────────────────────────────────────────────
library(JuliaConnectoR)
# First call downloads the library (takes a minute)
Effects <- juliaImport("Effects")
# Call `Effects.empairs` using R syntax `Effects$empairs()`
pairwise <- Effects$empairs(jmod2, dof = glance(jmod2)$df.residual)
pairwise
#> <Julia object of type DataFrames.DataFrame>
#> 15×7 DataFrame
#>  Row │ Gender  btype          r2: Y      err       dof    t          Pr(>|t|)  ⋯
#>      │ String  String         Float64    Float64   Int64  Float64    Float64   ⋯
#> ─────┼──────────────────────────────────────────────────────────────────────────
#>    1 │ F > M   curse          -0.404282  0.201612   7577  -2.00524   0.0449725 ⋯
#>    2 │ F       curse > scold   1.01214   0.13461    7577   7.51901   6.15243e-
#>    3 │ F > M   curse > scold   0.477022  0.196994   7577   2.4215    0.0154799
#>    4 │ F       curse > shout   1.77376   0.136284   7577  13.0152    2.57693e-
#>    5 │ F > M   curse > shout   1.90314   0.202352   7577   9.4051    6.75459e- ⋯
#>    6 │ M > F   curse > scold   1.41642   0.201127   7577   7.0424    2.05522e-
#>    7 │ M       curse > scold   0.881304  0.247263   7577   3.56424   0.0003671
#>    8 │ M > F   curse > shout   2.17805   0.202251   7577  10.769     7.53779e-
#>    9 │ M       curse > shout   2.30742   0.251552   7577   9.17273   5.84715e- ⋯
#>   10 │ F > M   scold          -0.535114  0.196498   7577  -2.72326   0.0064789
#>   11 │ F       scold > shout   0.761627  0.135565   7577   5.61817   1.99834e-
#>   12 │ F > M   scold > shout   0.891002  0.201868   7577   4.41378   1.02988e-
#>   13 │ M > F   scold > shout   1.29674   0.197648   7577   6.56086   5.70179e- ⋯
#>   14 │ M       scold > shout   1.42612   0.247866   7577   5.75357   9.07797e-
#>   15 │ F > M   shout           0.129376  0.202988   7577   0.637355  0.523913
#>                                                                 1 column omitted

Note that Julia DataFrame objects such as the one above can be collected into an R data frame using as.data.frame(). This lets you, for example, apply p-value corrections using the familiar p.adjust() function in R, though the option to do that exists in Julia as well.

pairwise_df <- as.data.frame(pairwise)
cbind(
  pairwise_df[, 1:2],
  round(pairwise_df[, 3:4], 2),
  pvalue = format.pval(p.adjust(pairwise_df[, 7], "bonferroni"), 1)
)
#>    Gender         btype r2..Y  err pvalue
#> 1   F > M         curse -0.40 0.20  0.675
#> 2       F curse > scold  1.01 0.13  9e-13
#> 3   F > M curse > scold  0.48 0.20  0.232
#> 4       F curse > shout  1.77 0.14 <2e-16
#> 5   F > M curse > shout  1.90 0.20 <2e-16
#> 6   M > F curse > scold  1.42 0.20  3e-11
#> 7       M curse > scold  0.88 0.25  0.006
#> 8   M > F curse > shout  2.18 0.20 <2e-16
#> 9       M curse > shout  2.31 0.25 <2e-16
#> 10  F > M         scold -0.54 0.20  0.097
#> 11      F scold > shout  0.76 0.14  3e-07
#> 12  F > M scold > shout  0.89 0.20  2e-04
#> 13  M > F scold > shout  1.30 0.20  9e-10
#> 14      M scold > shout  1.43 0.25  1e-07
#> 15  F > M         shout  0.13 0.20  1.000

Tips and tricks

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Displaying MixedModels

MixedModels.jl supports various display formats for mixed-effects models which are available in {jlme} via the format argument of print():

# Rendered via {knitr} with chunk option `results="asis"`
print(jmod, format = "markdown")
Est. SE z p σ_Subject
(Intercept) 251.4051 6.6323 37.91 <1e-99 23.7805
Days 10.4673 1.5022 6.97 <1e-11 5.7168
Residual 25.5918

Data type conversion

Be sure to pass integers (vs. doubles) to Julia functions that expect Integer type:

jl_put(1)
#> <Julia object of type Float64>
#> 1.0
jl_put(1L)
#> <Julia object of type Int64>
#> 1

The Dict (dictionary) data type is common and relevant for modelling workflows in Julia. {jlme} offers jl_dict() as an opinionated constructor for that usecase:

# Note use of `I()` to protect length-1 values as scalar
jl_dict(a = 1:2, b = "three", c = I(4.5))
#> <Julia object of type Dict{Symbol, Any}>
#> Dict{Symbol, Any} with 3 entries:
#>   :a => [1, 2]
#>   :b => ["three"]
#>   :c => 4.5

See ?JuliaConnectoR::`JuliaConnectoR-package` for a comprehensive list of data type conversion rules.

Performance (linear algebra backend)

Using MKL.jl or AppleAccelerate.jl may improve model fitting performance (but see the system requirements first). This should be supplied to the add argument to jlme_setup(), to ensure that they are loaded first, prior to other packages.

# Not run
jlme_setup(add = "MKL", restart = TRUE)
jlme_status() # Should now see MKL loaded here

Performance (data transfer)

If the data is large, a sizable overhead will come from transferring the data from R to Julia. If you are also looking to fit many models to the same data, you should first filter to keep only the columns you need and then use jl_data() to send the data to Julia. The Julia object can then be used in place of an R data frame.

data_r <- mtcars

# Keep only columns you need + convert with `jl_data()`
data_julia <- jl_data(data_r[, c("mpg", "am")])

jlm(mpg ~ am, data_julia)
#> <Julia object of type StatsModels.TableRegressionModel>
#> 
#> mpg ~ 1 + am
#> 
#> ────────────────────────────────────────────────────────────────────────
#>                 Coef.  Std. Error      z  Pr(>|z|)  Lower 95%  Upper 95%
#> ────────────────────────────────────────────────────────────────────────
#> (Intercept)  17.1474      1.1246   15.25    <1e-51   14.9432     19.3515
#> am            7.24494     1.76442   4.11    <1e-04    3.78674    10.7031
#> ────────────────────────────────────────────────────────────────────────

If your data has custom contrasts, you can use jl_contrasts() to also convert that to Julia first before passing it to the model.

data_r$am <- as.factor(data_r$am)
contrasts(data_r$am) <- contr.sum(2)

data_julia <- jl_data(data_r[, c("mpg", "am")])
contrasts_julia <- jl_contrasts(data_r)

jlm(mpg ~ am, data_julia, contrasts = contrasts_julia)
#> <Julia object of type StatsModels.TableRegressionModel>
#> 
#> mpg ~ 1 + am
#> 
#> ────────────────────────────────────────────────────────────────────────
#>                 Coef.  Std. Error      z  Pr(>|z|)  Lower 95%  Upper 95%
#> ────────────────────────────────────────────────────────────────────────
#> (Intercept)  20.7698     0.882211  23.54    <1e-99   19.0407    22.4989
#> am: 1        -3.62247    0.882211  -4.11    <1e-04   -5.35157   -1.89337
#> ────────────────────────────────────────────────────────────────────────

Just learn Julia

If you spend non-negligible time fitting regression models for your work, please just learn Julia! It’s a great high-level language that feels close to R in syntax and its REPL-based workflow.

Acknowledgments

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